The diagnosis of Pneumocystis infection can be made utilizing a variety of different staining procedures. These methods can be quite sensitive but require a high level of sophistication in the performance and interpretation of the tests. In addition, these stains are generally time consuming, including time to perform and time to read the stained smears. ELISA methodology is being used extensively now in the diagnosis of infectious agents. Methods have been simplified so that the test takes from minutes to a few hours to perform and requires no skill at interpretation since all one looks for is a color change in the reaction. We have 4 different monoclonal antibodies available to pursue this project. Attempts will be made to adapt one of these to an ELISA procedure, although it will take extensive developmental work in order to define the best procedure to obtain optimal sensitivity, sensitivity, rapidity and simplicity.